The CAS Registry Mumber 79974-13-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,9,9,7 and 4 respectively; the second part has 2 digits, 1 and 3 respectively. Calculate Digit Verification of CAS Registry Number 79974-13: (7*7)+(6*9)+(5*9)+(4*7)+(3*4)+(2*1)+(1*3)=193 193 % 10 = 3 So 79974-13-3 is a valid CAS Registry Number.